Value of Wood Finishes

Wood is used for its strength, ease of use and aesthetics. Two conditions influence the life of wood: weathering and decay. 

Weathering 

Weathering is erosion from sun, wind and debris, and moisture. If wood is not protected by paint or stain, the weathering process removes about ¼ inch of wood per century from softwoods on vertical exposures; even more wood is eroded in severe exposures.

The first step to prevent weathering is to block the sunlight. Finishes differ in their ability to protect wood from the sun. Paints can block sunlight completely, but they can trap moisture and encourage decay. Semitransparent stains are the next best way to block sunlight, followed by water-repellent preservatives, especially those that contain ultraviolet (UV) light inhibitors.

Decay

The other major service-life concern is decay (rot). Because outdoor wood is exposed to moisture, it is subject to decay. Decay, or rot, occurs due to the growth of specific fungi which feed on the fibres in the wood. Exposure to fungal spores that develop into fungi cannot be avoided as the spores are found everywhere. These spores will germinate and grow if the following four requirements are present:

. oxygen
. mild temperatures
. moisture, and
. suitable food (the wood).

For exposed wood structures, control over oxygen and temperature is not possible. However, control over moisture is possible. Eliminating this requirement will eliminate the potential for fungal growth and decay.

Protective Coatings 

One of the methods to eliminate moisture and ensure long life of wooden structures is to use protective coatings. Protective coatings for wood are used

. to enhance appearance

. to minimize ultraviolet degradation, and
. to protect against moisture exposure and fungal degradation.

Wood used in exterior applications needs to be protected and maintained periodically for a long life. As a general rule, recoating should be done when the previous finish is just beginning to show signs of aging, and before it loses its ability to protect the component.

A list of popularly used coatings for wood is below, graded by quality from low to high:

. Enamels - Solvent based

. Enamels - Water based

. Alkyd based coatings 

. Nitro-Cellulose Lacquers

. Epoxy Coatings

. Poly Urethane coatings(PU)

. Polyester coatings
 
Below is a table comparing a few of the wood finishes.

Why PU over other wood finishes.

Using quality fasteners

For any wooden structure to last, the joints have to be strong. Wood at joints are held in place using Fasteners. A good fastener not only guarantees strong and long lasting joints but also faster turn around times on projects. Fasteners such as 

. stainless steel nails 

. stainless steel screws and  

. galvanized nails 

 are recommended. 

These add only a fractional cost to a project when compared to lower quality products but turn out to be real money savers in the long term.